This invention relates generally to a ring-shaped element for a camera mechanism, and in particular to an improved locking-ring element formed from a metal sheet material wherein operating and engagement regions formed of synthetic material are selectively disposed about the ring and provide lubricating surfaces so that the ring may rotate about a fixed camera member.
Conventional metal rings for camera mechanism, such as shutters are suitable for providing the required dimensional accuracy. However, several disadvantages and shortcomings are inherent in the use of these metal rings in view of additional costly manufacturing steps. Initially, the metal rings are usually formed by punching from a metal sheet and the regions of the metal rings used for locking shutter parts have to be carefully worked and finished to provide the required surface quality. Without this additional working of the punched parts, the required dimensional accuracy cannot be achieved. An additional shortcoming of these conventional metal shutter rings is that it is not possible to punch the complicated operational and engagement regions from the metal sheet. These engagement areas are utilized for actuation of the camera mechanisms by rotation of the locking rings. It is generally only possible to form angled lugs or similar regions in the metal ring in one piece.
When one wishes to provide a complicated engagement region on an all-metal ring for activation of a camera mechanism, such as the shutter, additional manufacturing steps are required. It is not possible to form these complicated engagement regions in one piece at the time of formation of the ring. These complicated engagement regions must be added on to the ring after punching, such as by riveting or the like. An additional serious problem has always been a need for dimensional accuracy and consistency. These requirements generally are inconsistent with the need to use a formable material for the formation of operating surfaces, angle flaps, lugs or similar regions.
In order to overcome the above-mentioned disadvantages of metal rings, rings formed from synthetic materials have been proposed. Surely, such rings formed from synthetic material have the advantage that the desired engagement regions can be easily formed in the desired shape. However, when the rings are formed wholly of a synthetic material or if the synthetic material is applied as a shield about a metal ring, they must be formed thick in order to provide the required dimensional accuracy and consistency. Even when the synthetic material is a shield, shrinkage or contraction of the synthetic material leads to considerable inaccuracies. This makes these rings formed from synthetic materials unsuitable for use in place of the conventional metal rings. For these reasons, fast-moving locking rings formed from a synthetic material have not been acceptable. These inherent problems in the rings formed from synthetic materials arise even in slow-moving adjustable rings.
Accordingly, it would be desirable to provide a ring-shaped element for a camera mechanism which provides the high dimensional accuracy and consistency required. In addition, it would be desirable to provide such a locking-ring having as low a mass as possible and which does not need to be worked after forming. At the same time, it is desirable to provide rings having relatively complicated engagement regions which can be assembled in series in a space-saving construction.